PRNewsFotoMichael Jackson had a high tolerance for the powerful anesthetic that ultimately caused his death, according to testimony Thursday in the ongoing wrongful death trial in Los Angeles pitting his mother against concert promoter AEG Live.

One of Michael's many doctors testified that the singer would often receive 50 to 100 injections of Botox at a time. The doctor also said that Michael would be put to sleep using the anesthetic propofol during those injections. The levels of propofol administered to Michael increased over time because he had developed a higher tolerance for it, the doctor said.

Michael's mother, Katherine Jackson, filed a lawsuit against AEG, the concert promoter behind his aborted This Is It tour. She claims AEG contributed to her son's death by hiring Dr. Conrad Murray, who was convicted of involuntary manslaughter for giving Michael an overdose of propofol.